WO2016055292A1

WO2016055292A1 - Method and apparatus for processing a soy beverage product

Info

Publication number: WO2016055292A1
Application number: PCT/EP2015/072236
Authority: WO
Inventors: Birgitta Svensson; Sandra NILSSON
Original assignee: Tetra Laval Holdings & Finance S.A.
Priority date: 2014-10-08
Filing date: 2015-09-28
Publication date: 2016-04-14

Abstract

The invention relates to a method of processing a soy beverage product in a soy beverage product processing apparatus. Said method comprises the step of heat treating the soy beverage product. The method further comprises the steps of measuring the amount of undissolved gas present in the soy beverage product before the step of heat treating the soy beverage product, and if the amount exceeds a pre-set value, controlling the apparatus to de-aerate the soy beverage product, in order to decrease the amount of undissolved gas to a value at least below the pre-set value, before heat treating the soy beverage product, such that formation of dark particles in the soy beverage product can be avoided. The invention also relates to an apparatus.

Description

METHOD AND APPARATUS FOR PROCESSING A SOY BEVERAGE PRODUCT

TECHNICAL FIELD

The present invention relates to a method and apparatus for processing a soy beverage product.

BACKGROUND OF THE INVENTION

Within the field of human nutrition soy products have become more and more popular in recent years. Soy is a good source of protein for vegetarians and vegans, or for people who want to reduce the amount of meat they eat, since it contains significant amounts of all the essential amino acids. The protein ratio in soy is comparable to animal protein. Further, soy is considered a healthy nutrition due that it does not contain cholesterol and due to its low level of saturated fat. Soy products are furthermore lactose free making them suitable also for lactose intolerant people.

Soy-based food comes in many varieties such as soy milk, soy-based drinks, soy yoghurt, tofu, miso, tempeh and soy sauce. The raw material for producing soy-based food is whole soybeans. The soybeans are typically processed into a soy base, which soy base is then processed further into the various soy-based foods. An exemplary system for continuous extraction of soy base from whole or dehulled soybeans is marketed by the applicant under the registered trademark Tetra Alwin® Soy.

Common products processed in the Tetra Alwin® Soy system are soy beverages, in particular soy milk. Generally, a soy beverage such as soy milk is processed according to the following: Whole soybeans and hot water are supplied to a raw material intake unit. The mix of beans and water are fed to a grinding unit in which the mix is grinded into a slurry. The grinding is normally performed in two steps; first course grinding in for example a perforated disc mill, and then fine grinding in for example a colloid mill. In succeeding steps the slurry is processed in that soy proteins are extracted in a holding cell, the fibers are separated in a decanter and okara (i.e. soy pulp consisting of insoluble parts of the soybean) is discharged. The remainder, a clarified liquid soy base, is fed to a trypsin inhibitor inactivator in which the trypsin inhibitor of the soy is inactivated. In a next step the soy base is fed to a mixer for formulating a soy beverage product by mixing the slurry with water and sugar, and optionally other ingredients such as: salt, emulsifier and sodiumbicarbonate. The mixing may be made in for example a mixer marketed by the applicant under the registered trademark Tetra Almix®. Said mixer is a high shear mixer. After mixing the soy beverage product is optionally filtered. Filtering may be made by a slot strainer or one or two filters. In case the product is filtered twice a duplex filter may be used. Said filter is capable of filtering away any remaining particles of sizes > ΙΟΟμιη. After filtering the soy beverage product is further fed through a plate heat exchanger for cooling, and after cooling the soy beverage product is stored in a storage tank for about 1-2 hours. Before being packed into packaging containers, the soy beverage product undergoes a heat treatment, typically an ultra high temperature (UHT) treatment. This may be made in a system marketed by the application under the trademark Tetra Therm® Aseptic Flex. A such conventional UHT treatment comprises pre-heating the soy beverage product, homogenizing it at a temperature about 65-75°C and then heating it up to about 140°C during a final heating phase followed by a microbial reduction phase in which said high temperature is held for about 4s. The microbial reduction phase is followed by a two-step cooling.

It has recently been discovered that some unfortunate combinations of processing conditions or circumstances may give rise to presence of brown or dark particles in soy beverages after heat treatment. These particles have sizes of approximately 50-100 μιη (micrometer) and cannot be removed using a filter without affecting the product in a negative manner. One or few particles are difficult to perceive with the naked eye, and does not constitute a problem, but if there are many such particles present in one single packaging container, the soy beverage product looks discoloured. However, in most cases the particles are not harmful to consumers. SUMMARY OF THE INVENTION

Hence, an object of the present invention is to minimize the risk of dark particles arising in soy beverage products during processing thereof.

The object is solved by a method of processing a soy beverage product in a soy beverage product processing apparatus. The method comprises the steps of heat treating the soy beverage product, and the further steps of measuring the amount of undissolved gas present in the soy beverage product before the step of heat treating the soy beverage product, and if the amount exceeds a pre- set value, controlling the apparatus to de-aerate the soy beverage product, in order to decrease the amount of air bubbles to a value at least below the pre-set value, before heat treating the soy beverage product, such that formation of dark particles in the soy beverage product can be avoided.

It has been found that the brown or dark particles can be derived from air or gas bubbles covered by a protein layer. Some of the proteins, or amino acids, are hydrophobic and are likely to accumulate, together with sugar, on the boundary layer of bubbles of dispersed air, or any other undissolved gas, being present in the soy beverage product. During the final formulation of the soy beverage product air is inevitably mixed into the soy beverage product as bubbles. Some of the bubbles are sheared into micro bubbles, with a diameter about 100 μιη or less, during the mixing process. During the heat treatment, especially UHT treatment, these bubbles burst, leaving empty shells comprising accumulations of proteins and sugar. Upon further heating it has been found that said shells become brown or dark.

A risk in relation to common heat treatment, in particular UHT treatment, is Maillard browning of the product. It is caused by high temperature and can change the taste and smell of, in particular, dairy products or high protein products. As the name implies it can also cause browning of the product. Maillard browning is a chemical reaction between amino acids and sugars.

It is thus believed that the dark particles, that have been found in soy beverage products, are in fact accumulations of amino acids and sugar having changed colour due to a Maillard reaction during the heat treatment.

By measuring the amount of undissolved gas, for example the air bubbles, present in the soy beverage product prior to the UHT treatment appropriate measures can be taken to avoid accumulation of proteins, and thereby minimizing the risk of dark particles in the final product. One such measure is to de- aerate the soy beverage product before starting the UHT treatment. With de-aeration the amount of undissolved gas, e.g. air bubbles, can be decreased. De-aeration should in this context be broadly interpreted such as to encompass steps aiming to reduce the number of bubbles or micro bubbles in the soy beverage product.

In one or more embodiments the method comprises the step of de-aerating the soy beverage product by means of active de-aeration involving re-directing the soy beverage product to a de-aerator device.

In one or more embodiments the method comprises the step of de-aerating the soy beverage product by means of non-active de-aeration involving storing the soy beverage product in a tank.

Further, in one or more embodiments the step of heat treating the soy beverage involves performing an ultra high temperature treatment.

Furthermore, in one or more embodiments the step of measuring the amount of undissolved gas is made either in-line or off-line.

In one or more embodiments in-line measurement is performed by means of a sensor arranged in contact with the soy beverage product, which sensor is adapted to measure the percentage of undissolved gas in the product.

In one or more embodiments off-line measurement is performed by means of taking a sample volume of the soy beverage product at a sample station of the soy beverage product processing apparatus and measure the amount of undissolved gas in the sample volume.

In one or more embodiments the step of measuring the amount of undissolved gas is performed after performing a step of formulating and mixing soy beverage product ingredients. Further, in one or more embodiments measured undissolved gas is air bubbles in the soy beverage product.

In one or more embodiments the method comprises the step of: formulating and mixing soy beverage product ingredients by using a vaccum mixer.

In one or more embodiments the method comprises the steps of: supplying soybeans and water to the soy beverage product processing apparatus, grinding the soybeans and the water into slurry, separating fibres from the slurry to achieve a soy base, formulating the soy beverage product by mixing the soy base with at least water and sugar, and heat treating the formulated soy beverage product.

In one for more further embodiments the method further comprises the steps of extracting soy protein from the slurry, deactivating trypsin inhibitors in the soy base, and filtering and cooling the formulated soy beverage product.

The object is also solved by a soy beverage product processing apparatus of the invention. Said soy beverage product processing apparatus comprises a control device adapted for controlling the operation of the soy beverage product processing apparatus, a heat treatment device for heat treating the soy beverage product, and a measuring device adapted for measuring the amount of undissolved gas present in the soy beverage product. The measuring device is positioned upstream the heat treatment device. The apparatus further comprises a de-aeration device adapted to de-aerate the soy beverage product in order to decrease the amount of undissolved gas. If the amount of undissolved gas exceeds a pre-set value the control device is adapted to control the de-aeration device to decrease the amount of undissolved gas in the soy beverage product to an amount at least below the pre-set value, before the soy beverage product is fed to the heat treatment device, such that protein accumulation in the soy beverage product can be avoided.

In one or more embodiments the de-aeration device is non-active and comprises a storage tank, for storing the soy beverage product, said tank being located upstream the heat treatment device.

In one or more further embodiments the de-aeration device is active and comprises a de-aerator located upstream the heat treatment device.

Furthermore, in one or more embodiments the soy beverage product processing apparatus further comprises an intake device adapted to receive soybeans and water, a grinding device adapted to grind the soybeans and the water into slurry, a separation device adapted to separate fibres from the slurry to achieve a soy base, a mixing device adapted to mix the soy base with at least water and sugar for the formulation of the soy beverage product, and a heat treatment device adapted to heat treat the formulated soy beverage product.

In one or more embodiments the mixing device is a high shear mixer. In one or more embodiments the mixing device comprises a high shear, vacuum mixer.

In one or more embodiments the soy beverage product processing apparatus further comprises an extraction device adapted to extract soy protein from the slurry, a filtering device adapted to filter the formulated soy beverage product, a trypsin inhibitor deactivator, and a cooling device adapted to cool the formulated soy beverage device.

In one or more further embodiments the measuring device is a sensor adapted to be in contact with the soy beverage product, which sensor is adapted to measure the percentage of undissolved gas in the soy beverage product.

The object is also solved by a method of processing a soy beverage product in a soy beverage product processing apparatus, said method comprising the step of formulating the soy beverage product by means of a vacuum mixer in order to decrease the amount of undissolved gas, such that formation of dark particles in the soy beverage product can be minimised. BRIEF DESCRIPTION OF DRAWINGS

In the following, embodiments of the invention will be described in greater detail, with reference to the enclosed drawings, in which:

Fig 1 is a flow chart illustrating a general method of processing a soy beverage product in a soy beverage product processing apparatus.

Fig. 2 is a flow chart illustrating the method of the invention.

Fig. 3 is a flow chart illustrating the measuring step of the method of the invention.

DESCRIPTION OF EMBODIMENTS

With regard to the flow chart of Fig. 1 an exemplary and general method of processing a soy beverage product in a soy beverage product processing apparatus will now be described in greater detail. Naturally, a first step regards intake of raw material. The raw material is in this case dried, whole soybeans and hot water. The soybeans are supplied via a soybean hopper to a raw material intake unit. The water is prepared by heating it to a temperature around 55°C in a balance tank. From there it is fed to the raw material intake unit. In the raw material intake unit the soybeans will undergo a soaking step.

From the raw material intake unit the mix of beans and water are fed to a grinding unit in which the mix is grinded into slurry. The grinding step is performed in two steps. First a course grinding step is performed and then, in a succeeding step, fine grinding is performed. Accordingly, the grinding unit have two grinders or mills. The first, for performing the course grinding, is a perforated disc mill, and the second, for performing the fine grinding, is a colloid mill.

As a next step the grinded slurry of water and soybeans is fed to a holding cell to start extracting soy proteins from the fibres. The slurry is kept in a temperature of about 50-60°C in a pre-defined time before being fed to a decanter centrifuge for fibre separation. The decanter centrifuge can be of the single type, performing one decanter step, or of the double type, performing two consecutive decanter steps. Okara, i.e. soy pulp consisting of insoluble parts (fibres) of the soybean, is most often undesirable in the soy beverage product, hence it is discharged in this step.

After okara discharge the remainder is a clarified liquid soy base. The soy base is fed to a trypsin inhibitor deactivator in which the trypsin inhibitor enzyme of the soy is deactivated or inactivated. The deactivator comprises a holding cell with a steam injector. The steam injector is adapted to inject steam of 100°C.

Up to this point the process can be made continuous.

After the deactivation the soy base is optionally fed to a buffer storage tank awaiting the next processing step. During the storage the soy base is kept at about 95°C.

In a next step the soy base is fed to an in-line mixing device for formulating and mixing a soy beverage product. The mixing device comprises a mixing tank and a mixer. Normally, the mixer operates intermittently, producing a batch of formulated soy beverage product at a time. The mixer is a high shear mixer. It mixes the soy base with water and sugar, and optionally other ingredients such as salt, emulsifier and stabilizer. During the addition of ingredients in the mixer some air is inevitably mixed into the soy beverage product. For soy beverage products this is more difficult due to the high degree of proteins. Proteins are generally foam-stabilizing, which means that the air bubbles will stabilize into foam at the product's surface or form stable micro bubbles in the product.

After the mixing step the soy beverage product is optionally fed to a filtration unit for filtering away any remaining and unwanted particles. The filtration unit may comprise one or two filters. For example, in the case of two filters, a first filter adapted to remove particles in sizes > 150μιη and a second filter adapted to remove particles in sizes >

ΙΟΟμιη. The filtration unit may instead comprise a slot strainer. Micro bubbles of air will typically pass through the filters or slot strainer.

After filtering the soy beverage product is fed through a conventional plate heat exchanger for cooling. The soy beverage product is cooled down to about 10-20°C, and after cooling it is generally fed to a storage tank adapted to buffer a couple of batches of soy beverage product. Typically, at least three to four batches of soy beverage product are produced and stored before commencing to the next step, the heat treatment. This is due to the fact that the heat treatment unit normally has a higher capacity than the mixer. This can of course be compensated for by having additional mixers in the processing apparatus.

The next step in the processing of the soy beverage product is, as mentioned, to let it undergo a heat treatment, e.g. an ultra high temperature (UHT) treatment for the purpose of sterilizing the soy beverage product. A typical UHT treatment comprises pre -heating the soy beverage product by means of a tubular heat exchanger, homogenizing it at a temperature about 65-75°C in a homogenizer, heating it up to about 140°C during a final heating phase in another tubular heat exchanger, and keeping the high temperature for about 4-15 seconds in a holding tank as a microbial reduction phase. The heating steps are followed by a two-step cooling in two different tubular heat exchangers.

The UHT treatment completes the processing of the soy beverage product and product is ready to be packed into packaging containers, for example paper-based packaging laminate containers.

The invention suggests adding processing steps to the above process in order improve it by minimizing the risk of protein accumulations, as described in the

introductory part, in the finished product. One such processing step involves determining the presence of undissolved gas in the product, in particular the amount of air bubbles present, and a second such processing step involves de-aerating the soy beverage product before heat treatment. Fig. 2 shows a flow chart of the method of the invention, comprising these additional processing steps.

The step of measuring the amount of undissolved gas present in the soy beverage product can be made at a number of alternative measuring points. Exemplary measuring points are shown as boxes marked with Mi, M_2, M₃, M₄ and M₅ respectively. All the shown measuring points Mi, M_2, M₃, M₄ and M₅ are arranged upstream the heat treatment. Mi is arranged right after the mixing step, and is thus arranged in for example the outlet tube from the mixing tank. M₂ is arranged downstream Mi before the cooling step, in the inlet tube to the plate heat exchanger. M₃ is arranged after the cooling step, in the outlet tube of the plate heat exchanger. M₄ is arranged just before heat treatment step in the tube leading to the first tubular heat exchanger of the heat treatment station. M₅ differs from the others in that it is not situated in a tube but in a storage tank located before the heat treatment. M₅ may comprise a bundle of measurement points arranged at different levels in the tank.

A processing apparatus of the invention needs to be provided with at least one measuring point, preferably at least one of Mi, M_2, M₃, M₄ and M₅. Alternatively, another measurement point can be arranged at another location in the processing apparatus if that is to prefer due to space limitation, an alternative order of processing steps etc. Further, more than one measurement point can be arranged in one processing apparatus for measurement at two or more stages in the process. The step of measuring the amount of dissolved gas is made either in-line or offline. The in-line measurement is performed by means of providing a sensor in contact with the soy beverage product flow, i.e. providing a sensor, in one or more of the measurement points, in the conduit or tube in which the product flows. The measurement can be made continuously during operation or be made intermittently at pre-determined intervals. The sensor used is adapted to measure the percentage of undissolved gas, e.g. air bubbles or micro bubbles, in the product.

There are various commercial sensors that are able to detect the amount of undissolved gas or air in a product flow through a tube or in a tank filled with product, and which can be used in the present invention. For example, there is a sensor, marketed by CiDRA Minerals Processing, named Sonartrac GVF-100, which sensor is adapted to measure the gas volume fraction in a flowing product by means of sound. Noise from pumps, valves etc create acoustic waves which travel with the flow and against the flow. The sensor, which is formed as an array of detectors, measures the speed at which the acoustic waves pass through the sensor in order to determine the sound speed of the combination of undissolved air and product. The measured sound speed is then correlated to the fraction of the undissolved air.

Another commercial sensor that may be used is Oxymax COS22/22D marketed by Endress & Hausser. The measuring technology is electrochemical and the sensor reacts on oxygen molecules, which makes it applicable if the undissolved gas to be detected is air. The oxygen molecules are diffused through a membrane and are reduced to hydroxide ions (OH ) at a cathode of the sensor. Silver is oxidized to silver ions (Ag⁺) at an anode of the sensor. A detectable current will flow due to the electron donation at the cathode and the electron acceptance at the anode. Under constant conditions, this flow is proportional to the content of oxygen in the product. Endress & Hausser is also marketing a sensor named Proline Promass 80 which can be alternatively used. The measuring technique is based on density measurements and measurements of excitation energy.

A further potential sensor for detecting the amount of oxygen in the product is Orbisphere Ml 100 marketed by Hach Lange. Its measuring technique is based on luminescence. An active fluorescent area is excited with blue light. Red luminescent light is detected. If oxygen is present the rate of fluorescence decay is changed and this directly relates to an oxygen partial pressure value.

The above sensors are examples of potential sensors to be used. It should be understood that other sensors able to detect the amount of undissolved air or gas in a product are of course also possible.

The off-line measurement is performed by means of taking a sample volume of the soy beverage product at a sample station of the soy beverage product processing apparatus and measure the amount of undissolved gas in the sample volume. The sample stations are equal to the measurement points Mi, M_2j M₃, M₄ and M₅. The sample stations can be of any conventional type used for taking a sample from the product being processed in the apparatus. One of the simplest ways of determining the amount of undissolved gas in the sample is to pour it in a measuring glass having a relatively large volume compared to the glass diameter. The level of the sample volume is measured in the glass and the sample is left in the glass until the gas bubbles have reached the surface of the sample. The surface level of the liquid product is measured, i.e. not the level of any potential foam or surface bubbles, and is compared to the initial measurement. From the two measurements the percentage of undissolved gas in the product can be assessed. Another way of making an off-line measurement of a sample volume is to use a camera and a microscope. The camera is used to take an image in the sample volume and the microscope is used to analyse the number and sizes of bubbles in the image. The analysis can be automatically made by for example an image recognition software or similar. Further, this method can be turned into an in-line measurement method as well, provided the volume of the sample can be determined.

Common for in-line and off-line measurements is that the measured value is compared to a pre-set value. In in-line measurements the comparison is preferably made by a control device, for example the PLC, controlling the processing apparatus. In off-line measurements the comparison can for example be manually made. Fig. 3 illustrates the basic flow chart for the step of measuring the amount of undissolved gas.

If the amount of undissolved gas, i.e. amount of air bubbles, in the soy beverage product is lower than or equal to the pre-set value the risk of dark particles in the final soy beverage product is low. Hence, the soy beverage product can proceed to the heat treatment step without any additional de-aeration being made. The soy beverage product may however be subject to conventional storage in a buffer tank depending on the configuration of the processing apparatus.

If the amount of undissolved gas in the soy beverage product exceeds the pre-set value there is a high risk of dark particles in the final soy beverage product if it proceeds to the heat treatment step without de-aeration. Hence, if the measured value exceeds the pre- set value, the processing apparatus is controlled in such a way that the soy beverage product is subject to de-aeration. The purpose of the de-aeration is to decrease the amount of air bubbles to a value below the pre-set value, before heat treating the product. In this way protein accumulation in the soy beverage product can be avoided. The necessary de- aeration time will naturally be dependent on the configuration of the processing method and the processing apparatus and will have to be tested for each individual method and apparatus. In an apparatus where the measurement is made in-line, any de-aeration is preferably controlled by the control unit of the processing apparatus. In an apparatus where the measurement is instead made off-line, an operator may initiate proper de-aeration steps. The step of de-aerating the soy beverage product can be made in various ways in the processing apparatus. For example, the de-aeration can be made either active or non- active. Active de-aeration involves re-directing the soy beverage product to a de-aerator device. There are various conventional de-aerator devices that can be used.

A de-aeration method commonly used in the processing field is to make use of a vacuum de-aeration in an expansion vessel connected to vacuum. The liquid is transported to the expansion vessel with a certain temperature which is some degrees above the boiling point at the pressure prevailing in the expansion vessel. When the liquid enters the vessel via a valve and the temperature and pressure conditions in the vessel causes it to instantly start boiling, a process referred to as flash boiling. The process results in that liquid is vaporized and that air is released during flashing. Liquid vapor condense against cooled areas in the vessel, while the released air is evacuated from the vessel by the vacuum pump, while the liquid exits through an opening in the bottom of the vessel. In order to increase the separation rate the liquid may enter the expansion vessel in a tangential direction, so as to induce a swirl.

Another applicable de-aeration method that can be applied is described in the international publication WO2013/037796, which is hereby incorporated by reference. The de-aeration method involves subjecting the fluid to an instantaneous and significant pressure drop. Such a pressure drop will induce nucleation. Experiments reveal that the nucleation of (gas) bubbles occurs in the entire volume of the fluid, i.e. a homogenous nucleation, and that it therefore facilitates an efficient de-aeration. The method comprises the steps of pressurizing the soy beverage product to a pressure above atmospheric, guiding it through a nucleation valve, and lowering the pressure on a downstream side of the valve to a sub-atmospheric pressure. As liquid passes the nucleation valve bubble nucleation is caused, which is the first step of the de-aeration. The temperature and pressure on the downstream side of the valve is controlled such that the static pressure is above the saturation pressure, while the lowest pressure as the liquid passes the valve is below or equal to the saturation pressure.

Other de-aerator devices, suitable for de-aerating gas bubbles from a liquid, can of course be used.

To obtain a safe and effective process, active de-aeration is preferably made when the soy beverage product is still warm, around 60-80°C. Hence, as can be seen in Fig. 2, it is preferably made after the optional filtering step, i.e. before the cooling step, at numeral 2 in Fig. 2. This is particularly effective if any of the measurement points Mi and M₂ is used for measuring the amount of undissolved air.

An additional way of actively de-aerating, i.e. reducing the amount of undissolved air in the soy beverage product, is to perform the mixing step in a high shear, vacuum mixer. The low pressure, obtained by a vacuum pump, prevailing in the mixer will minimize the amount of air being mixed into the soy beverage product. The step of using a vacuum mixer may be combined with the other active de-aerating steps described above, and with the non-active de-aerating steps to be described in the following.

As mentioned above non-active de-aeration can instead be used. Non-active de- aeration simply means storing, i.e. the soy beverage product is stored in a tank for a period of time. Preferably, the storage time is long enough for the soy beverage product to reach equilibrium, i.e. a state in which the undissolved air has been able to escape to the surface level of the soy beverage product in the tank. In reality, total equilibrium is not desirable, but the storage time need at least to be long enough to decrease the amount of bubbles down to a value below the pre-set value, at least near the outlet of the tank. The necessary storage time will depend on many factors, e.g. the volume of the tank, the volume of the soy beverage product, the type of soy beverage product, the pressure prevailing in the tank and the pre-set value etc.

Non-active de-aeration tanks, i.e. storage or buffer tanks, can be arranged at various positions in the processing apparatus to serve the purpose of de-aerating the soy beverage product before heat treatment.

The de-aeration step of a first embodiment is illustrated by the numeral 1 in Fig. 2. Here the de-aeration is solved in that the processing apparatus has more than one mixing tank that can also be used for storage. If the apparatus is provided with two mixing tanks they can be alternately used. One prepares a new batch of soy beverage product while the other acts as storage tank for de-aeration of the previously prepared batch.

The de-aeration step of a second embodiment is illustrated by the numeral 2 in Fig. 2. Here the soy beverage product is instead re-directed to one or more storage tanks for de- aeration after the filtering step, i.e. before the cooling step. This is particularly effective if any of the measurements point Mi and M₂ is used for measuring the amount of undissolved air.

The de-aeration step of a third embodiment is illustrated by the numeral 3 in Fig. 2. De-aeration is here made just before the heat treatment. Here there is normally a storage step and hence there is provided an intermediate storage tank, or buffer tank, for accumulation of product batches to be heat treated. In some applications the normal storage or buffer time that the soy beverage product spends in the tank is enough to achieve necessary de-aeration. In other applications more time is needed, and one or more additional tanks are provided. In such way at least two tanks can be alternately used for storage and supply to the heat treatment respectively. If de-aeration is made just before the heat treatment, measurement points M₃, M₄ or M₅ are preferably used for the detection of the amount of undissolved air, but also the previous measurement points Mi and M₂ may be used. If the tank is large and used for accumulation of many batches (one batch = the content of one mixing tank) of soy beverage products measurement in the tank, i.e.

measurement point M₅, may be preferred. Bubbles will gather at the surface of the tank. In many tanks the inlet is placed in the top whereas the outlet is placed in the bottom of the tank. When filling for example second and third batches of soy beverage product into the tank, from above, there may be created intermediate layers of bubbles which will strive towards the product surface. With a bundle of sensors in the tank, at different levels, it is possible to detect where these layers of bubbles exist and how fast they move upwards. The volume of soy beverage product underneath the lowermost layer of bubbles is de- aerated, i.e. has an amount of bubbles less than the pre-set value, and may be discharged for further processing downstream the tank. Two or more parallel tanks may be used alternately to increase the possible de-aeration time.

Both active and non-active de-aeration have been described and it should be understood that both de-aeration methods can be combined in one processing apparatus. Further, it has been shown that de-aeration, particularly non-active de-aeration, can be performed at various places in the processing apparatus. Also here a combination is possible, i.e. part of the de-aeration is made for example at numeral 2, and part of the de- aeration is made for example at numeral 3.

It is apparent to a person skilled in the art that the described embodiments are examples and that various modifications are possible. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

It should be pointed out once more that the above described general processing method is exemplary. There are other methods of processing soy beverage products in which the processing steps and their order may differ from the described embodiment. For example, inactivation of trypsin inhibitors may be made already after grinding by cooking the slurry. After cooking the slurry is filtered to extract the soy base. Filtration is made using a decanter centrifuge. After that a deodorisation step may be performed, and the protein content may be adjusted. The soy base is then formulated into a soy beverage in a mixing step, or a formulation step, where the soy base is enriched with sugar and flavours. A subsequent step may be homogenization to obtain the desired consistency and formulation. For soy beverages to be distributed in a chilled environment, the final heat treatment may be pasteurization instead of UHT treatment.

In the described example the raw material is dried soy beans. However, soy beverage products can be manufactured starting from another source of soy for example isolated soy protein, soy protein concentrate, soy flour and dried soy powder. This will of course alter some of the early processing steps.

Claims

1. Method of processing a soy beverage product in a soy beverage product processing apparatus, said method comprising the step of

heat treating the soy beverage product, and wherein the method further comprises the steps of:

measuring the amount of undissolved gas present in the soy beverage product before the step of heat treating the soy beverage product, and if the amount exceeds a preset value,

controlling the apparatus to de-aerate the soy beverage product, in order to decrease the amount of undissolved gas to a value at least below the pre-set value, before heat treating the soy beverage product, such that formation of dark particles in the soy beverage product can be avoided.

2. The method according to claim 1, wherein the method comprises the step of de- aerating the soy beverage product by means of active de-aeration involving re-directing the soy beverage product to a de-aerator device.

3. The method according to claim 1, wherein the method comprises the step of de- aerating the soy beverage product by means of non-active de-aeration involving storing the soy beverage product in a tank.

4. The method according to any of the preceding claims, wherein the step of heat treating the soy beverage involves performing an ultra high temperature treatment.

5. The method according to any of the preceding claims, wherein the step of measuring the amount of undissolved gas is made either in-line or off-line.

6. The method according to claim 5, wherein in-line measurement is performed by means of a sensor arranged in contact with the soy beverage product, which sensor is adapted to measure the percentage of undissolved gas in the product.

7. The method according to claim 5, wherein off-line measurement is performed by means of taking a sample volume of the soy beverage product at a sample station of the soy beverage product processing apparatus and measure the amount of undissolved gas in the sample volume.

8. The method according to any of claims 1-7, wherein the step of measuring the amount of undissolved gas is performed after performing a step of formulating and mixing soy beverage product ingredients.

9. The method according to any of claims 1-8, wherein measured undissolved gas is air bubbles in the soy beverage product.

10. The method according to any of claims 1-9, wherein the method comprises the step of: formulating and mixing soy beverage product ingredients by using a vaccum mixer.

11. The method according to any of the preceding claims 1-10, wherein the method comprises the steps of:

supplying soybeans and water to the soy beverage product processing apparatus, grinding the soybeans and the water into a slurry,

separating fibers from the slurry to achieve a soy base,

formulating the soy beverage product by mixing the soy base with at least water and sugar, and

heat treating the formulated soy beverage product.

12. Soy beverage product processing apparatus comprising

a control device adapted for controlling the operation of the soy beverage product processing apparatus,

a heat treatment device for heat treating the soy beverage product, and wherein the soy beverage processing apparatus further comprising

a measuring device adapted for measuring the amount of undissolved gas present in the soy beverage product, wherein said measuring device is positioned upstream the heat treatment device,

a de-aeration device adapted to de-aerate the soy beverage product in order to decrease the amount of undissolved gas, and

wherein the control device, if the amount of undissolved gas exceeds a pre- set value, is adapted to control the de-aeration device to decrease the amount of undissolved gas in the soy beverage product to an amount at least below the pre- set value, before the soy beverage product is fed to the heat treatment device, such that formation of dark particles in the soy beverage product can be avoided.

13. The soy beverage product processing apparatus according to claim 12, wherein the de-aeration device is non-active and comprises a storage tank, for storing the soy beverage product, said tank being located upstream the heat treatment device.

14. The soy beverage product processing apparatus according to claim 12, wherein the de-aeration device is active and comprises a de-aerator located upstream the heat treatment device.

15. The soy beverage product processing apparatus according to any of the claims 12- 14, wherein the soy beverage product processing apparatus further comprises

an intake device adapted to receive soybeans and water,

a grinding device adapted to grind the soybeans and the water into slurry, a separation device adapted to separate fibres from the slurry to achieve a soy base, a mixing device adapted to mix the soy base with at least water and sugar for the formulation of the soy beverage product, and

a heat treatment device adapted to heat treat the formulated soy beverage product.

16. The soy beverage product processing apparatus according to claim 15, wherein the mixing device comprises a high shear mixer.

17. The soy beverage product processing apparatus according to claim 16, wherein the mixing device comprises a high shear, vacuum mixer.

18. The method according to any of the claims 12-17, wherein the measuring device is a sensor adapted to be in contact with the soy beverage product, which sensor is adapted to measure the percentage of undissolved gas in the soy beverage product.